1. The problem statement, all variables and given/known data Consider a circuit which output is the absolute value of the input signal, this is, y(t)=|x(t)|? a) this circuit is not a LIT system because it implements a non linear operation; b) this circuit is a LIT system that creates phase distortion; c) this circuit is a LIT system that creates amplitude distortion; d) this circuit is a LIT system that creates amplitude and phase distortion. 2. Relevant equations -- 3. The attempt at a solution My first thought was... it's not linear because it will "convert" only the negative part of the sinusoid but then... isn't this because of the phase? I can't decide between a) and b). Could someone please give a help?